In a disk drive the electromagnetic heads are each resiliently mounted on the end of a flexible cantilever arm forming part of a linear or rotary actuator. Each flexible cantilever arm projects between a pair of disks in a disk stack to move the heads in track seeking and track following operations. When the disk drive is not in operation the actuator moves the heads to parked positions. In one parking mode the heads are parked on the disk surface in a head parking zone next to the hub of the disk stack. In another parking mode the actuator removes the armstack and the heads from a position between the disks to a position removed from the disks onto a parking ramp at the edge of disk stack.
The disk drives are designed to withstand the shock forces which are usually encountered in a normal operational environment, but when being handled or moved, shock forces from bumping or dropping, in the absence of suitable restraints or displacement limiters, may result in damaging displacements or deflections of the structural parts and/or collisions of parts.
Prior art restraints in disk drives include actuator limit stops such as crash stops and latches, For limiting extremes of actuator displacements and for securing the actuator in that extreme of displacement in which magnetic heads are parked. U.S. Pat. Nos. 4,538,193; 4,647,997; 4,692,892 and 5,036,416, describes such general types of actuator restraints or locks.
Unlike the patents above, U.S. Pat. No. 4,939,611 assigned to the assignee of this invention, describes a vertical limit stop or crash stop which is disposed between the disks at the peripheral edges whenever the actuator is moved to a position in which the magnetic heads are parked on the disk surfaces adjacent the hub of the disk stack. This vertical limit stop prevents collisions between the individual arm stacks and the adjacent closely spaced disk surfaces in the presence of shock forces having force components paralleling the disk stack axis.
While this type of vertical limit stop is effective in limiting relative movement between the disks and the arm stack structure to obviate arm stack disk collisions it does not limit magnetic head displacements.
None of the limit stops described in the referenced patents address the matter of head/disk collisions.